/Engine/Plugins/Runtime/NetworkPrediction/Source/NetworkPrediction/Public/NetworkPredictionSerialization.h
The Fixed/Independent ticking implementations are a more than trivially different so they are split into separate implementations. Both currently send the last 'NumInputsPerSend' per serialization, determined from config settings. This could be improved with something more dynamic.
template<typename InModelDef> class TFixedTickReplicator_Server